The invention relates to an infinitely variable traction roller transmission in which power is transmitted through traction rollers pivotally supported in a housing between toric input and output discs.
In such transmissions, the traction rollers are mounted on support structures which, when pivoted, cause engagement of the traction rollers with the toric discs in circles of varying diameters depending on the desired transmission ratio. The pivotal traction rollers are so supported that they can be moved axially for initiating a change in the transmission ratio. For example, two traction rollers may be supported opposite one another by flexible tension sheets as shown in U.S. Pat. No. 4,086,820 which issued May 2, 1978 to Charles E. Kraus.
However, the forces applied to the traction rollers and, through the traction roller support structure, to the tension sheets are substantial and, consequently require support structure of great strength together with adequate pivot bearings therefor.
In the arrangement according to U.S. Pat. Nos. 4,484,487 and 4,576,055 also assigned to the assignee of the present application, the traction roller support structure is therefore hydraulically supported directly on the housing so that the support structure is not subjected to bending forces. Pivoting of the opposite roller support structures for appropriate transmission ratio positions may be coordinated by an interconnecting ribbon as shown in U.S. Pat. No. 4,086,820, for example.
This arrangement is quite effective and inexpensive for support structures disposed at a given distance from one another but cannot readily be used where the pivoting support structures are floatingly supported as they are in the arrangements shown in U.S. Pat. Nos. 4,484,487 and 4,576,055 since their distance from one another may change somewhat during operation of the transmission.
Also, it is pointed out that the arrangements described in the above patents utilize two traction rollers. For transmission of higher power however, more than two traction rollers, that is, for example, four traction rollers arranged in pairs with two disposed diametrically opposite one another may be provided. With such an arrangement however there is no room for tension sheet supports nor for coordinating ribbons or ropes in the transmission since they would all interfere with one another.